JP2002048615A - Flowmeter using thermal flow sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately display an integrated amount of gas consumption by, with a simple configuration, instantaneously judging occurrence of pulsation in the rate of flow, which is to be measured, and excluding effect of the pulsation through a passing flow-rate calculation. SOLUTION: A micro heater 53 is provided in a flow path where a fluid flows. At least two pairs of temperature sensors are provided which comprise two thermo piles 55, 57, 59a and 59b respectively arranged in symmetry on the upper stream side and the lower stream side of the micro heater 53. Related to the thermo piles 55, 57, 59a and 69b, the pairs are arranged by different distance from the heater, respectively, and the difference in voltage between the temperature sensors at different distances is used as a base for detecting presence of the pulsation in the fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter using a heat flow sensor capable of reducing an error in a flow rate caused by pulsation and accurately displaying the amount of gas used.

[0002]

2. Description of the Related Art Conventionally, as this type of flow meter, there is, for example, a flow meter disclosed in Japanese Patent Application Laid-Open No. Hei 5-157597. This flow meter outputs, from the A / D converter, an output pulse Ps obtained by adding a fixed pulse number to a pulse number proportional to the flow rate detected by the heat flow sensor and performing zero shift as a signal B.

Then, the magnitude determination circuit determines the magnitude relationship between the fixed pulse number Po generated by the pulse generator and the pulse number Ps of the signal B, and the gas flow is positive (Ps> Po).
Or backflow (Ps <Po). According to this determination result, the smaller of the pulse numbers Po and Ps is subtracted from the larger one, and | Ps−Po | is calculated by the calculation circuit.
The calculation result is added or subtracted in the calculation circuit depending on whether the flow of the gas, which is the result of the determination by the magnitude determination circuit, is the normal flow or the reverse flow, and the integrated flow rate value is calculated.

FIG. 6 is a view schematically showing an electronic gas meter using a conventional thermal flow sensor. Micro flow sensor (heat flow sensor) in this gas meter GM
Reference numeral 5 denotes a base on which a micro heater 53 for heating is arranged on a base 51 made of silicon Si, and the bases are equally spaced at both ends of the micro heater 53 in the flow direction A of the gas flowing in the gas flow path 3. A thermopile 57 for upstream and downstream for temperature measurement is arranged on 51.

When the heat generated by the micro heater 53, which is energized from the power source 7 through the switching transistor 9, is transmitted to the vicinity of the thermopiles 55, 57 using the gas in the gas flow path 3 as a medium, the heat generated from the thermopiles 55, 57 is changed. An electromotive force of a voltage according to the temperature is generated. The difference in voltage due to the electromotive force of each of the thermopiles 55 and 57 depends on the flow velocity of the gas flowing through the gas passage 3 or the gas pipe.

The voltage difference is digitally converted by the A / D converter, and then input to the microcomputer 13 for processing. Finally, the integrated amount of gas flowing in the gas pipe is obtained and displayed on the display unit 15. You.

[0007]

Some combustors that consume gas supplied through an electronic gas meter cause pressure fluctuations in the supplied gas pressure during use. For example, in the case of a GHP (gas heat pump), its use causes a fluctuation in gas pressure at a frequency of 10 to 20 HZ, which causes the gas flow to change with time as shown in FIG. Pulsation occurs.

[0008] When the flow velocity of such a pulsating gas flow is measured at a sampling interval of a fixed period, and the passing flow rate is obtained based on the measured flow velocity, the accurate flow velocity is not always accurate depending on the pulsation period and the sampling time. There was a problem in that the flow rate could not be measured, and an error occurred in the flow rate obtained from the flow rate, and a flow rate different from the actual gas consumption was calculated.

In order to solve such a problem, the sampling period may be reduced at all times. However, in this case, the power consumption increases, and when the gas meter is powered by a battery, the period for replacing the battery is shortened. The problem of being uneconomical cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a simple configuration and determines that a pulsation has occurred in the flow velocity to be measured instantaneously, and calculates the pulsation based on the passing flow rate. It is an object of the present invention to provide a flow meter using a heat flow sensor capable of accurately integrating and displaying a gas usage amount while eliminating the influence of pulsation.

[0011]

A flow meter using a thermal type flow sensor according to the present invention has a heater installed in a flow path of a fluid as shown in a basic configuration diagram of FIG. At least two pairs of temperature sensors comprising two temperature sensors symmetrically arranged on the upstream side and the downstream side of the heater are provided, and the distances from the heaters are different for each group. And detecting the presence of a pulsation in the fluid based on a voltage difference between the temperature sensors at different distances.

According to the present invention, there is provided at least a temperature sensor having a heater installed in a flow path of a fluid and comprising two temperature sensors symmetrically arranged on the upstream side and the downstream side of the heater. Two sets of flow sensors, second input means for inputting a voltage difference according to the flow velocity of the fluid between the temperature sensors having different distances, and voltage difference data under a steady flow between the temperature sensors having different distances in advance. Storage means for storing, a comparing means for comparing the voltage difference inputted from the second input means with the stored voltage difference data,
A determination unit that determines whether there is pulsation in the fluid at the time of determination of a mismatch from the comparison result, and when there is pulsation in the fluid, the flow rate based on the voltage difference according to the flow velocity of the fluid between the temperature sensors having the same distance. Restrict operations.

According to the present invention, a first input means for inputting a voltage difference between two temperature sensors symmetrically arranged on an upstream side and a downstream side of a heater, respectively, based on a determination result of the determination means, An averaging means for averaging the voltage difference inputted from the first input means, and a flow rate calculating means for calculating a flow rate of the fluid based on the averaged voltage difference, wherein a pulsation exists in the fluid. The flow rate is calculated after averaging the voltage difference according to the flow velocity of the fluid between the temperature sensors having the same distance to eliminate the pulsation component.

The present invention further comprises invalidating means for invalidating a voltage difference inputted from the first input means based on a result of the judgment by the judging means. The voltage difference according to the flow velocity of the fluid is nullified.

According to the present invention, the distance from the heater to each of the temperature sensors is set in accordance with the expected amplitude of the pulsation, and the pulsation component is detected by the level change of each voltage difference.

The storage means of the present invention stores each voltage difference data according to the speed of the fluid, and the comparison means retrieves the voltage difference data according to the fluid speed from the storage means, and obtains different voltage difference data according to the fluid speed. The presence of the pulsating component is detected by comparing the voltage difference of the electric power with the voltage difference data corresponding to the stored fluid velocity.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Next, a flow meter using the heat flow sensor according to the present embodiment will be described with reference to the accompanying drawings. FIG. 2 is a schematic configuration diagram of an electronic gas meter GM using the heat flow sensor according to the present embodiment.
In the drawing, the same reference numerals as those in FIG. 6 indicate the same or corresponding parts. In the figure, 5A is a heat flow sensor whose detailed configuration is shown in FIG. In this heat flow sensor 5A, a micro heater 53 for heating is arranged on a base 51 made of silicon Si, and the both ends of the micro heater 53 in the gas flow direction A in the gas flow direction 3 are equally spaced from each other. And upstream and downstream thermopiles 55, 57 for temperature measurement are arranged on a base 51, and
A second upstream thermopile 59b is provided on the upstream side of the upstream thermopile 57, and a second downstream thermopile 5 is provided on the downstream side of the downstream thermopile 57.
9a is arranged for pulsation detection.

In the thermal type flow sensor 5A having such a configuration, the microcomputer 13 supplies the switching transistor 9
, A constant-voltage power from the power supply 7 is continuously supplied to the micro heater 53, and the micro heater 53 is heated.

Then, an upstream thermopile 59 located upstream of the micro heater 53 in the gas flow direction.
Heat released from the micro heater 53 is propagated to b and 55 at a speed obtained by subtracting the gas flow speed from the gas heat propagation speed. Further, downstream thermopiles 57, 59a located downstream of the micro heater 53 in the gas flow direction.
The heat released from the micro-heater 53 is propagated at a speed obtained by adding the gas flow speed to the heat propagation speed of the gas.

Therefore, if gas is not flowing in the gas flow path 3, the upstream thermopile 55, the downstream thermopile 57, and the second upstream thermopile 59b,
Since the second downstream thermopiles 59a are respectively located at equal intervals from the microheater 53, heat of the same temperature is applied to the upstream thermopile 55 and the downstream thermopile 57 from the microheater 53, and The same temperature heat is transmitted from the micro heater 53 to the upstream thermopile 59b and the second downstream thermopile 59a.

However, the thermopiles 59b and 59a are farther from the microheater 53 than the thermopiles 55 and 57, and therefore have lower temperature rise sensitivity. Therefore, the voltage of the electromotive force generated in the thermopiles 59b and 59a is different from the voltage of the electromotive force generated in the thermopiles 55 and 57. Therefore, when the gas is not flowing, the voltage difference between the thermopiles 55 and 57 is substantially 0, but the thermopiles 59b and 55,
A voltage difference occurs between 57 and 59a due to a difference in sensitivity to temperature rise.

However, when the gas flows in the gas flow path 3, the heat released from the micro heater 53 is transmitted to the upstream thermopiles 55, 59b at a lower speed than the propagation speed to the downstream thermopiles 57, 59a. The heat from the micro-heater 53 is transferred to the thermopile 59b, 55 on the upstream side by the speed difference and the thermopile 57, 55,
59a, the voltage of the electromotive force generated in each of the upstream and downstream thermopiles 55, 57 depends on the temperature difference of the heat transmitted from the micro heater 53 by the gas flowing through the gas flow path 3. , That is, according to the flow velocity of the gas flowing in the gas flow path 3.

Also, the second upstream thermopile 59
(b) The second thermopile 59a on the second downstream side is farther from the micro heater 53 and therefore has a lower temperature rise sensitivity, so that the voltage due to the electromotive force is lower than that of the adjacent thermopiles 55 and 57. Therefore, the voltage difference V between the thermopiles 55 and 57
0, the voltage difference VD1 between the thermopiles 59b and 55, and the voltage difference VD2 between the thermopiles 57 and 59b are different in the steady flow of gas.

In such a thermopile arrangement, the voltage difference between the upstream thermopile 55 and the downstream thermopile 57 is digitally converted by the A / D converter 11 and taken into the microcomputer 13. In addition, the voltage difference between the upstream thermopiles 59b and 55 and the voltage difference between the downstream thermopiles 57 and 59a, and in some cases, the voltage difference between the upstream thermopile 59b and the downstream thermopile 59a are also determined by the A / D converter 11. The digitally converted data is taken into the microcomputer 13.

RAM constituting microcomputer 13 shown in FIG.
13a has a data area for storing various data and a work area used for various processing operations. ROM13
b includes a program for performing a pulsation detection process, an averaging process, and a flow rate calculation process based on the flow velocity, and between the thermopiles 59b and 55 in a steady flow in which the gas flow velocity does not change due to the fluctuation of the gas pressure, and 57 and The voltage difference VD1, VD2, V0 or VD3 data between 59a is stored for each flow rate.

The CPU 13A which constitutes the microcomputer 13 has a voltage difference V0, VD1, VD which is a sensor output output from the thermal flow sensor 5 via the A / D converter 11.
2 or VD3, for example, the voltage difference VD
1, VD2 and the voltage differences VD1 and VD2 under steady flow at a predetermined flow rate stored in the ROM 13b, and if it is determined that these voltage differences do not match, the voltage difference V0 used in the flow rate calculation is shown in FIG. It is determined that the pulsation shown in FIG. 3 (b) exists, the voltage difference V0 is averaged to remove the pulsation, and then the instantaneous flow velocity of the gas flowing in the gas flow path 3 is obtained.

The instantaneous flow velocity obtained as described above is multiplied by a predetermined coefficient or the like depending on the cross-sectional area of the gas flow path 3 and the structure of the gas flow path 3 to obtain the flow rate of the gas flowing through the gas flow path 3. Find the instantaneous flow rate. Further, by multiplying the instantaneous flow rate by the cycle time for intermittently outputting the drive signal of the micro heater 53, the cycle time from one output of the drive signal of the micro heater 53 to the next output of the drive signal is obtained. During this time, the flow rate of the gas flowing in the gas flow path 3 is obtained, and the flow rate is integrated to obtain the integrated flow rate of the gas flowing in the gas flow path 3.

The operation of this embodiment will be described below with reference to the flowchart shown in FIG. First, each of the voltage differences V0 and, for example, the voltage differences VD1 and VD from the thermal flow sensor 5A.
2 is taken in as a flow velocity signal (step S1). Also,
The respective voltage differences VD1 and VD2 under a steady flow are read from the ROM 13b as reference signals (step S3). The flow rate signal is compared with the reference signal to determine whether the signals match (step S4).

If it is determined in step S4 that the signals match, it is determined that there is no pulsating component in the voltage difference V0 for flow measurement, and the voltage difference V0 is taken in as the instantaneous gas flow velocity. Then, as described above, the flow rate of the gas that has passed through the gas flow path is calculated by multiplying the flow velocity of the gas by the cross-sectional area of the flow path, and this flow rate is integrated to obtain the integrated gas flow rate, that is, the gas supply amount ( The gas usage is obtained and displayed on the display unit 15 (step S5).

However, if it is not determined in step S4 that the flow velocity signal matches the reference signal, it is determined that the pulsation component exists in the flow measurement voltage difference V0, and the pulsation component is removed from the flow velocity signal. It is determined whether to perform the averaging process (step S7). If it is determined that the averaging process is to be performed, the flow rate signal having the voltage difference V0 is averaged to remove a pulsation component (step S9).
The flow rate is calculated (step S). However, if it is determined that the averaging process is not to be performed, the input flow velocity signal is invalidated and the flow velocity signal is waited for.

As described above, when the voltage differences VD1 and VD2 stored in advance as the reference signals are compared with the actually measured voltage differences VD1 and VD2 as the flow velocity signals, when the respective signals match, the pulsation component is included in the flow velocity signal. By judging that the pulsation does not exist, the pulsation can be detected more accurately and instantaneously than by actually sampling the voltage difference V0 between the upstream thermopile 55 and the downstream thermopile 57 and detecting the pulsation.

If a pulsating component exists in the voltage difference V0 and the sampling period is synchronized with, for example, the peak of the pulsating component, there is a possibility that the peak level voltage difference is erroneously detected while the pulsating component exists. . In addition, if the sampling time is increased to prevent such erroneous detection, the calculation speed of the flow rate decreases.

However, as in the present embodiment, both the voltage differences VD1 and VD2 stored as the reference signals and the actually measured voltage differences VD1 and VD2 as the flow velocity signal are generated when the pulsation component exists in the flow velocity signal. Since there is no possibility that they coincide with each other, a pulsation component can be instantaneously detected due to the inconsistency of both signals.

In the above description, the thermopiles 59b and 5
5 and the gap between the thermopiles 59a and 57 are not particularly mentioned, but the pulsation amplitude may be predicted to some extent, and the gap may be set so that the peak-to-peak of the waveform appears as a voltage difference. As a result, the voltage difference V0 that is the flow velocity signal is obtained.
Pulsation can be detected more instantaneously than sampling pulsation. Further, the voltage differences VD1, VD2,
The pulsation can be detected with high accuracy by setting the sampling frequency for detecting VD3 by predicting the pulsation frequency.

[0035]

According to the present invention, there is provided a pair of temperature sensors having a heater installed in a flow path of a fluid, and comprising two temperature sensors symmetrically arranged on the upstream and downstream sides of the heater. At least two sets of temperature sensors are provided, each set having a different distance from the heater for each set, and detecting the presence of pulsation in the fluid based on a voltage difference between the different temperature sensors. By doing so, there is an effect that it is possible to determine instantaneously that pulsation has occurred in the flow velocity to be measured, with a simple configuration.

According to the present invention, a temperature sensor having a heater installed in a flow path of a fluid and comprising two temperature sensors symmetrically arranged on the upstream side and the downstream side of the heater, respectively. , A second input means for inputting a voltage difference according to the flow velocity of the fluid between the temperature sensors having different distances, and voltage difference data under a steady flow between the temperature sensors having different distances. And a comparing means for comparing the voltage difference input from the second input means with the stored voltage difference data. Based on the result of the comparison, it is determined that there is a pulsation in the fluid at the time of mismatch determination. Determining means for judging, when a pulsation exists in the fluid, by restricting a flow rate calculation based on a voltage difference according to the flow velocity of the fluid between the temperature sensors having the same distance, the pulsation component There is an effect that the amount of erroneous operation can be prevented.

According to the present invention, the first input means for inputting the voltage difference between the two temperature sensors symmetrically disposed on the upstream side and the downstream side of the heater, respectively, Averaging means for averaging a voltage difference inputted from the first input means, a flow rate calculating means for calculating a flow rate of the fluid based on the averaged voltage difference, and a display unit for displaying a flow rate calculation result When there is pulsation in the fluid, the flow rate calculation is accurately performed by averaging the voltage difference according to the flow velocity of the fluid between the temperature sensors having the same distance to eliminate the pulsation component and performing the flow rate calculation. There is an effect that can be performed.

According to the present invention, there is provided a temperature sensor provided with a nullifying means for nullifying a voltage difference inputted from the first input means based on a judgment result by the judging means, and in a case where pulsation exists in the fluid, the temperature sensors are equal in distance The voltage difference according to the flow velocity of the fluid is invalidated, and the next voltage difference having no pulsation component is taken in, whereby the reliability of the calculation of the integrated flow rate is improved.

According to the present invention, the pulsation component is set by setting the distance from the heater to each of the temperature sensors in accordance with the expected amplitude of the pulsation and detecting the pulsation component based on the level change of each voltage difference. There is an effect that the detection of is easy.

According to the present invention, the storage means stores each voltage difference data according to the speed of the fluid, and the comparison means retrieves the voltage difference data according to the fluid speed from the storage means.
By detecting the presence of a pulsating component by comparing the voltage difference of the electromotive force different according to the fluid velocity and the stored voltage difference data according to the fluid velocity, based on the voltage difference regardless of the fluid velocity change There is an effect that a pulsation component can be detected.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a flow meter using a thermal flow sensor according to the present invention.

FIG. 2 is a schematic configuration diagram of a gas meter using a flow meter using the thermal flow sensor according to the present embodiment.

FIG. 3 is an enlarged view showing a configuration of a thermal flow sensor according to the present embodiment.

FIG. 4 is an electrical configuration diagram mainly showing a microcomputer of a flow meter using the thermal flow sensor according to the present embodiment.

FIG. 5 is an RO of the microcomputer shown in FIG. 4;
5 is a flowchart showing a flow rate calculation program stored in M.

FIG. 6 is a schematic configuration diagram of a gas meter using a flow meter using a conventional thermal flow sensor.

[Explanation of symbols]

 51 flow sensor 13a1 first input means 13a2 second input means 13c comparing means 13e determining means 13f invalidating means 13g averaging means 13h flow rate calculating means 15 display unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mitsuyoshi Anzai 1500 Onjuku, Susono-shi, Shizuoka Yazaki Sogyo Co., Ltd.F-term (reference)

Claims (6)

[Claims] At least two pairs of temperature sensors each having a heater installed in a flow path of a fluid and having two temperature sensors symmetrically arranged on the upstream side and the downstream side of the heater, respectively. And arranging each temperature sensor so that the distance from the heater is different for each set, and detecting the presence of pulsation in the fluid based on a voltage difference between the temperature sensors having different distances. Flow meter using a heat flow sensor. 2. At least two pairs of temperature sensors each having a heater installed in a flow path of a fluid and comprising two temperature sensors symmetrically arranged on the upstream and downstream sides of the heater, respectively. A flow sensor provided, second input means for inputting a voltage difference according to the flow velocity of the fluid between the temperature sensors having different distances, and voltage difference data under a steady flow between the temperature sensors having different distances are stored in advance. Storage means, comparing means for comparing the voltage difference inputted from the second input means with the stored voltage difference data, and judging means for judging that there is a pulsation in the fluid at the time of discrepancy judging from the comparison result And a flow meter using the heat flow sensor. A first input unit for inputting a voltage difference between two temperature sensors symmetrically arranged on an upstream side and a downstream side of the heater, and a determination result of the determination unit. An averaging means for averaging the voltage difference input from the first input means, a flow rate calculating means for calculating a flow rate of the fluid based on the averaged voltage difference, and a display unit for displaying a calculation result. A flow meter using the heat flow sensor according to claim 2. 4. The heat flow sensor according to claim 2, further comprising invalidating means for invalidating a voltage difference input from the first input means based on a result of the determination by the determining means. Flow meter. 5. The flowmeter according to claim 1, wherein a distance from the heater to each of the temperature sensors is set in accordance with a pulsation amplitude. 6. The apparatus according to claim 2, wherein said storage means stores each voltage difference data according to the speed of said fluid, and said comparison means retrieves said voltage difference data according to the fluid speed from said storage means. A flow meter using the heat flow sensor according to any one of claims 1 to 4.